While BART workers and trains were off track for the four days of the recent strike, vandals were busy tagging stations, trains and buildings, including San Francisco's Glen Park Station, which was covered with graffiti.

Graffiti vandals hit nine locations scattered around the 104-mile system between Friday and Monday when stations were closed, train service was halted, and fewer eyes were keeping watch.

Glen Park looked to be the hardest hit, Fairow said, though it could cost more to fix vandalism at other locations. At Glen Park, taggers marred walls, floors, signs, stairs, advertisements and benches. They also tagged on and above the electrified third rails.

Cleanup started at 10 a.m. Tuesday, about four hours after BART resumed service, and was still in progress Wednesday, said Alicia Trost, a BART spokeswoman.

"The problem is that there's a lot of it, some of it's on marble, which is harder to clean, and some is on the trackway, where it can't be cleaned when trains are running," she said.

Other spots targeted by graffiti vandals include the Richmond yard; the Millbrae staging area; the Balboa Park, 19th Street/Oakland and Bay Fair stations; a maintenance access area between the Balboa Park and Glen Park stations in San Francisco; the Concord yard; and the North Berkeley tunnel.

Two men were arrested for felony vandalism after they were caught tagging railcars in the Richmond yard Saturday, Fairow said. They were identified as Hubani Hernandez, 23, of San Pablo, and Zachary Borders, 25, of San Francisco.

Investigations into all of the incidents are continuing, Fairow said, and it's not clear whether any of them are connected. All involved graffiti vandalism, but some fencing was cut to gain access to BART property.

Some taggers hit BART during the July strike, so BART police deployed more officers to the system's yards, where trains are stored. But the force was stretched thin, Fairow said, especially after the accident that killed two workers between the Walnut Creek and Pleasant Hill stations Saturday.